One attractive and popular type of sign structure currently available today is a sign in which a sheet of flexible sign material is held in tension across the opening of a suitable frame. Signs of this type can be easily and economically changed and also permit the legends and graphics to be applied to the membrane at a different location and easily installed at the location of the sign. Signs of this type are also relatively inexpensive and quite durable. A variety of signs of this type have been shown in the prior art, such as in U.S. Pat. Nos. 3,885,335; 4,185,408; 4,265,039; 4,372,071; and 4,580,361.
A useful way of constructing signs of this type is to provide a plurality of tensioning devices which are spaced around the outer periphery of the support frame rearwardly of the frame opening which is defined by the edges of the frame sides. Typically, however, the prior art tensioning devices require the turning of a screw or other threaded fastener which is a relatively slow, time consuming, manual manipulation. Often these screws are not accessible except from the front of the sign and typically engage in holes at fixed position along the frame and therefore cannot be slid laterally to assist in the removal of wrinkles as the sign membrane is tensioned. Structures of this type are shown in U.S. Pat. Nos. 4,452,000; 4,554,754; and 4,674,214.
One difficulty with tensioning devices of this nature is that they typically require that the membrane be laid upon the frame and fitted to the tensioning devices. As a result, the membrane, when initially connected to the tensioning devices, is drooped across the opening of the frame. This results in excess, slack material positioned between the tensioning devices which must be taken up by the tensioning devices. Unless the slack is taken up perfectly uniformly, wrinkles occur. The result is that a substantial effort is required to remove the wrinkles and properly adjust the membrane. In addition, the conventional tensioning devices cannot be slid laterally to assist in the removal of those wrinkles.
One advantage of the present invention is that the sign membrane may be laid upon a flat, planar surface and the frame laid upon the membrane. The membrane is thus held in a relatively planar shape, similar to its position when tensioned, thus minimizing the excess, slack material which must be taken up later.
Another advantage of the present invention is that the tensioning device of the present invention is extremely easy to manipulate, both in tensioning the material and in sliding the tensioning devices laterally in order to help remove wrinkles.
Yet another advantage of the tensioning devices of the present invention is that they permit the membrane to be loosely attached and captured on the frame before significant tension is applied so that the material is held loosely in place before more precise tensioning is attempted.
Another advantage of the present invention is that its tensioning devices permit a broad range of adjustment and a substantial improvement in the ease and speed with which the sign membrane can be preliminarily attached to the sign frame and the ease and speed with which tensioning is accomplished. Tensioning is accomplished not by the twisting of a screw driver or other similar adjustment, but merely by a simple push from a human finger.
Still another feature and advantage of the present invention is that it is applicable to the tensioning of a broad variety of other membranes, such as the attachment of boat covers on boats, and has further advantages as a simple mechanical connector, such as for use as a picture or other object hanger.